Method and apparatus for preventing surging in a blower or the like



3,157,349 URGING 1964 MATSUKI lTAYA ETAL METHOD AND APPARATUS FOR PREVENTING S IN A BLOWER OR THE LIKE Filed Aug. 7. 1962 INVENTORS 3 M4 730K! 174K IIIDETOJIII 41/14! a n a 54/6 Ell! Til/J! BY a. 6:44

United States Patent 3,157,349 METHCD AND APPARATUS FOR PREVENTENG SURGING EN A BLOWER OR THE LHKE Matsulri Itaya, 61 Qhohayama, Meguro-hu; Hidetoshi Kusarna, 83 Kamimeguro=i-chome; and dhigeru Tsuji, 24-1 Denenchofu-l-chome, all of Tokyo, .lapan Filed Aug. '7, i962, Ser. No. 232,319 Claims priority, application Japan, 0st. 2, 1%57, 24-,189/ 57 9 Claims. (Cl. 230-115) This invention relates in general to blowers and the operation thereof, and in particular to a new and useful device for adjusting the flow through a blower in order to insure that the blower does not operate under surging conditions.

The present application is a continuation-in-part application of my copending application Serial No. 753,553 filed August 6, 1958 for Method and an Apparatus for Preventing Surging in a Blower or the Like, now abancloned.

Prior to the present invention, blowers have been known to operate in a manner in which the speed of the blower increased and decreased in a surging manner in accordance with the pressure conditions to which the blower suction and discharge lines were subjected. In order to prevent surging of blowers of this type, some systems include means for releasing air for recirculating fluid from the discharge of the blower back to the suction or inlet in proportions to regulate the operation of the blower so that surging will not occur. A great disadvantage of systems of this character is that the blower must always be operated at a greater capacity than necessary in order that the surging be prevented. This, of course, represents a waste of power since a great deal of the portion of the blower power is employed for preventing surging.

In accordance with the present invention, there is provided an automatic means for adjusting the flow in the suction line of a blower in accordance with a novel arrangement for sensing pressure on each side of a damper or valve control damper in order to regulate the damper and vary the pressure conditions on the suction of the blower.

In a preferred arrangement, a surge preventing valve is located in the suction line leading to the blower and is operated automatically in such a manner that the characteristic curve of the total pressure is maintained in such relation to the capacity of the blower that surging does not occur. Such a characteristic curve shows total pressure head versus the capacity or volumetric flow of the blower and, in the region of the low operating capacity, it indicates that a tangent drawn to the curve is not larger than that limited for maintaining a dynamic stability in the operation of the blower. I

A feature of the inventive construction is that a simple means is provided for sensing pressure on each side of a control damper and for automatically regulating the position of the damper in the suction line for varying flow capacity of such line instantaneously in accordance with such pressure conditions so that the blower will operate in a uniform manner and without surging.

The invention advantageously includes a diaphragm which is subjected to pressure on opposite sides of the damper control and which is arranged to direct a nozzle fluid jet in one direction or another to influence a servomotor connected to the damper for changing the position thereof between various stages of open and closed.

Accordingly, it is an object of this invention to provide an improved blower control device.

A further object of the invention is to provide a device for regulating the operation of a blower to insure that the blower operates without surging and including a damper control means positioned in the suction line to such blower and with pressure sensing devices on each side of the damper arranged to effect adjustment of the damper to maintain uniform flow conditions and operation of the blower.

A further object of the invention is to provide a control device for the operation of a blower which includes a suction line having an adjustable damper therein and including means on each side of the valve for sensing the pressure in the suction line and connected to diaphragm means for operating a servo-motor for shifting the valve in accordance with the pressure which has been sensed.

A further object of the invention is to provide a device for controlling surging in a blower and the like which is simple in design, rugged in construction and economical to manufacture.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which there is illustrated and described a preferred embodiment of the invention.

In the drawings:

FIG. 1 is a curve indicating the characteristics of a blower showing the variation of capacity and pressures; and

FIG. 2 is a schematic indication of a suction line damper and pressure sensing regulator therefor as constructed in accordance with the invention.

- Referring to the drawings in particular, there is indicated in FIG. 1 a characteristic curve for a blower in which pressure developed is indicated on the ordinate and the change in capacity is indicated on the abscissa. It can be seen that, with an increase in capacity, the pressure first increases and then reaches a peak, and lastly decreases.

In accordance with the present invention, a surge preventing valve or damper generally designated 2 (see FIG. 2) is arranged in a suction line 1 leading to a blower 3 in a manner to be operated automatically so that the characteristic curve indicated by the letters A, B, C and D in FIG. 1 has a tangent less than that represented by the line A, B, C, maintained less for preventing surging in the low capacity operation surging region which occurs at the location of the portion of the curve A, B, C.

According to the present invention, power loss due to a required pressure drop by the surge-preventing valve 2, and the .curves A, B, C, B, A, become remarkably smaller than those corresponding to a surge-preventing valve arranged in the discharge channel of the blower.

A further advantage of arranging a valve of this character in the suction is that there is no tendency that overthrottling of the valve will cause an intense resurging, since such resurging does not occur even in over-throttling the valve.

In FIG. 2, the surge-preventing apparatus is indicated, which includes the valve or damper 2 located in the suction line 1 of the blower 3 which is driven by the motor 4. The conduit 5 is the discharge of the blower 3.

In accordance with the invention, pressure sensing lines or conduits 6 and '7 are disposed to sense pressure on opposite sides of the valve 2 at locations indicated at I1 3 charged under pressure through a nozzle tip portion 11a. A compression spring normally biases the jet pipe 11 in a direction toward the diaphragm 8 and flexing of the diaphragm in an opposite direction must overcome the compression force of the spring.

The jet pipe is arranged so that it pivots about a pivot point 11b to swing the discharge 11a to direct oil under pressure either to an opening 13 or to an opening 14 in pipes or conduits 15 or 16, respectively, which lead to alternate sides of a cylinder 17 of a servo motor to move a piston 17a therein to one side or the other. Movement of the piston 17a is effective to open and close the valve 2 by rotating rod 19a connected to the valve. The rod 19 is pivoted to a link 18 fixed to the rotating axis of a link 18a with whose free end is connected the piston rod 17b of the piston 17a.

Regulation of the degree of shifting of the valve 2 in accordance with the pressure condition sensed at 11 and 11 may be made by means of an adjustment generally designated 34 comprising a wedge element which is movable upwardly or downwardly to displace a plunger 20a slidable in a sleeve extension 36 to change the compression force of the spring 10.

With the arrangement described, the surge preventing valve 2 is operated automatically in such a manner that the pressure dilference it between the pressures I1 and I2 before and behind the valve 2 is maintained for each capacity of the blower 3 at an amount greater than the specific minimum resistance pressure 12 necessary for preventing surging. For example, if the control system of a constant value resistance is used so that, in the region A, F of the curve indicated at the bottom of the graph in FIG. 1, a smaller capacity of a blower is indicated, the surge preventing valve 2 is prevented by an adjustable stopper 38 from closing fully. Thus, the opening degree of the valve 2 is maintained constant while for a capacity larger than that corresponding to F, the pressure difference 11 between the pressures I1 and 11 before and after the valve 2 is maintained at a constant value h which is larger than h and hence the surging of the blower can be prevented perfectly.

It was found experimentally that in the case of the inventive construction, the resistance pressure loss h amounted to only 1% of the maximum pressure of the blower. It should be appreciated that the connections between the levers 18 and 19a may be adjusted as well as the wedge member 20 to vary the elastic force of the spring 10 and to equalize each required resistance pressure to reach specific minimum resistance pressure 11 necessary for each capacity of the blower.

While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that this invention may be embodied otherwise without departing from such principles.

What is claimed is:

1. In a variable capacity blower including a suction line and a discharge line, said blower requiring a minimum of resistance pressure in said suction line to prevent surging of said blower, the improvement comprising means for preventing surging of said blower including adjustable pressure loss resistance means disposed in said suction line, means to sense pressure in said suction line on each side of said adjustable pressure loss resistance means, and control means connected to said pressure sensing means and to said adjustable pressure loss resistance means to adjust said pressure loss resistance means to maintain a pressure difference between each side of said adjustable pressure loss resistance means at a value above the minimum resistance pressure to prevent surging.

2. In a variable capacity blower according to claim 1, wherein said adjustable pressure loss resistance means is a valve.

3. In a variable capacity blower according to claim 2, including a stopper operable to limit closing movement of said valve to a pre-set partially open position to prevent it from fully closing during low blower capacities.

4. In a variable capacity blower according to claim 1, wherein such pressure sensing means includes a flexible diaphragm, and means for directing pressure from one side of said adjustable pressure loss resistance means to one side of said diaphragm and from the other side of said pressure loss resistance means to the other side of said diaphragm.

5. In a variable capacity blower according to claim 4, wherein said flow resistance device is a valve and including a servo-motor connected to said valve and movable in accordance with movement of said diaphragm to regulate the disposition of said valve in said suction line.

6. In a variable capacity blower according to claim 5, wherein said servo-motor includes a cylinder and a piston slidable therein connected to said valve, and pivotally mounted high pressure jet means connected to said diaphragm and movable thereby between a position pressurizing one side of said servo-motor cylinder to a position pressurizing the opposite side of said servo-motor.

7. In a variable capacity blower according to claim 6, including adjustable spring means biasing said high pressure jet means and said diaphragm to stabilize said diaphragm in a neutral position.

8. In a variable capacity blower including a suction line and requiring a minimum flow resistance in said suction line to prevent surging of said blower; surge preventing means comprising, in combination, an adjustable flow resistance device in said suction line; sensing means operable to sense the pressure differential across said device; and control means interconnecting said sensing means and said device and operable, responsive to variation of such pressure differential from an adjustable pre-set value at least equal to the value corresponding to said minimum flow resistance, to adjust said device to restore said pressure difierential to such pre-set value.

9. In a variable capacity blower, surge preventing means as claimed in claim 8, said sensing means comprising a flexible diaphragm device; means for applying pressure upstream of said flow resistance device to one side of said diaphragm device; and means for applying pressure downstream of said flow resistance device to the other side of said diaphragm device; said control means including an element connected to and movable with said diaphragm device.

References Cited in the tile of this patent UNITED STATES PATENTS 1,487,402 Roucka Mar. 18, 1924 1,566,850 Frenne Dec. 22, 1925 2,012,978 Veensc'noten Sept. 3, 1935 2,490,188 Ziebolz Dec. 6, 1949 3,014,493 Seger Dec. 26, 1962 FOREIGN PATENTS 109,611 Great Britain Dec. 24, 1918 390,150 Germany Jan. 31, 1922 

1. IN A VARIABLE CAPACITY BLOWER INCLUDING A SUCTION LINE AND A DISCHARGE LINE, SAID BLOWER REQUIRING A MINIMUM OF RESISTANCE PRESSURE IN SAID SUCTION LINE TO PREVENT SURGING OF SAID BLOWER, THE IMPROVEMENT COMPRISING MEANS FOR PREVENTING SURGING OF SAID BLOWER INCLUDING ADJUSTABLE PRESSURE LOSS RESISTANCE MEANS DISPOSED IN SAID SUCTION LINE, MEANS TO SENSE PRESSURE IN SAID SUCTION LINE ON EACH SIDE OF SAID ADJUSTABLE PRESSURE LOSS RESISTANCE MEANS, AND CONTROL MEANS CONNECTED TO SAID PRESSURE SENSING MEANS AND TO SAID ADJUSTABLE PRESSURE LOSS RESISTANCE MEANS TO ADJUST SAID PRESSURE LOSS RESISTANCE MEANS TO MAINTAIN A PRESSURE DIFFERENCE BETWEEN EACH SIDE OF SAID ADJUSTABLE PRESSURE LOSS RESISTANCE MEANS AT A VALUE ABOVE THE MINIMUM RESISTANCE PRESSURE TO PREVENT SURGING. 